Removal of metal halides from fluids



m Nm om J. w. LArcHuM, JR., E-rAl.

REMOVAL OF METAL HALIDES FROM FLUIDS Filed Jan. 3, 1944 vows.. am

Jan. 30, 1945.

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aNoz Nouvzawosl INVENTOR J. w. LATcHuM,JR. BY J. auf-HAM A'rro NE JOI Patented 30, 1945 REMOVAL 0F METAL HALIDES FROM FLUlDS John W. Latchum, Jr., and John D. Upham, Bartlesvill e, Okla., assignors to Phillips Petroleum Company, a corporation of Delaware Application January s, 1944, serial No. 516,884

14 Claims.

This invention relates to the removal of. metal halides from iluids. A specic modification of the invention relates to purification of fluid reaction eiiluents from hydrocarbon conversionsv carried out in the presence of an anhydrous, normally solid or liquid, metal halide of the Friedellyst permeates the entire system causing numerous troubles including corrosion, further reaction, clogging, etc. This is especially objectionable in ythose sections of the equipment which follow the conversion unit. Thus, where the eiiluent is removed in the vapor phase and. as is almost invariably the case where' catalysts of the type described above are used, where the catalyst is readily volatilizable, the eflluent contains substantial quantities of vaporized catalyst, and this catalyst in processes heretofore practiced deposits in the equipment after the converter. Vaporous eiiluents also ordinarily carry small but appreciable amounts of liquid metal halide sludge out of the reaction chambers by entrainment.

Numerous solutions to the problems presented in conversions of the type described have been proposed, but very few have found success in actual practice. A method which has been highly successful is the scrubbing of vaporous isomerization or other conversion effluents with sulfuric acid, which ellects complete removal of vaporized aluminum chloride as well as any entrained sludge. Such a process is disclosedby John W.

Latchum, Jr. in patent application Serial No. 460,858, filed October 5, 1942. In a somewhat similar manner phosphoric acid lmay be'used as described in application Serial No. 460,859, led October 5, 1942, by John W. Latchum, Jr. The present invention may be considered as an improvement over the processes of the Latchum applications just referred to.

In the use of sulfuric or phosphoric acid to scrub fluids having free aluminum chloride or other metal halide contained therein, gaseous hydrogen halide is formed and aluminum sulfate or other metal sulfate or phosphateis 'precipitated in the acid in the form of a finely divided (Cl. 26o-683.5)

moved from the acid and represents, together with the hydrogen halide, substantially the only spending of the acid which occurs. However, when entrained aluminum chloride sludge is carried by theA fluids into the acid scrubber, reaction occurs between the sludge and the acid to form hydrogen chloride and aluminum sulfate and also to form reaction products between the sulfuric acid and the organic constituents of the sludge.

.These latter reaction products are of a nature which is not fully understood at the present time; however, it is known that from hydrolysis of the acid, alcohols of relatively high molecular weight may be obtained. In addition, sulfonates and the like are believed to be formed to a substantial extent.

Such reaction of acid with sludge is highly desirable in that the 4sludge is not only removed from the conversioniiuids, which is the primary function of the acid scrubbing, but also in that the inorganic and organic constituents thereof are also recovered in useable form. However, the acid is spent at a much more rapid rate by reaction with the sludge, than by the reaction with free volatilized aluminum chloride. Furthermore, the acid upon reaction with the sludge becomes very dark colored and it is contaminated otherwise remain in a relatively pure condition for longer periods of operation.

It is an object of our invention to remove` Friedel-Crafts type metall halides from iluids, particularly from gaseous paraln hydrocarbons.

Another object is to improve an acid scrubbing system of the type described, wherein a strong, relatively non-volatile mineral acid is used, so as to give longer acid life and cleaner acid for re'- circulation. y

Another object is to remove aluminum chloride sludge from entrainment in gaseous butane isomerization ellluents.

A still further object is to provide a two-stage solid. This solid is readily settled out and re- 5s process for purifying hydrocarbon conversion streams carrying volatilized and suspended metal halides and metal halide sludges.

Yet another object is to recover valuable components from metal halides and metal halide sludges.

A still further object is to provide a longer catalyst life for a supported aluminum chloride isomerization catalyst.

Further objects and advantages of the invention will be apparent, to one skilled inthe art,

, from the accompanying disclosure and description.

Due to its importance, and for the sake of convenience, the invention will be described with particular reference to the isomerization of normal butane to produce isobutane in which the reaction mixture is passed in vapor state through primary and secondary catalyst ,chambers containing solid aluminum chloride catalysts. Application of the principles of the invention to other conversions may readily be made by suitable modiflcations by oneskilled in the art. As a means of illustrating a preferred and specific embodiment of the invention, the accompanying drawing is provided, which shows in somewhat diagrammatic form one arrangement of apparatus and flow of materials therethrough, in which the process f the invention may be practiced. It will beA appreciated that in view of the schematic nature of the drawing numerous items of auxiliary equipment such as heaters, contactors, pumps, valves, control equipment, fractionators, etc. have been omitted, for they may readily be supplied by one skilled in the art.

In the drawing, tworeaction chambers III-'and I2 are provided. The primary reaction zone I 0 contains lump aluminum chloride while the second zone contains a calcined low-iron-content bauxite, such as that sold under the trade name of .Porocel Other solid adsorbent material such as activated charcoal, fullers earth, silica gel,

lactivated alumina, natural and articial zeolites,

various natural and synthetically prepared claylike materials, etc. may be used in a manner known to the art. Normal butane, vaporized and heated (by means not shown) to a desired reaction temperature such as 195 F., enters the system through line I3 and is joined by a gaseous stream of hydrogen chloride activator introduced through line I4 in amounts which may, for example, correspond to from two to ten mol per cent of the total feed. The gaseous reaction mixture passes through isomerization zone Il wherein a partial conversion to isobutane is eil'ected. A limited amount of aluminum chloride becomes incorporated in the vapors by sublimation. The resulting gases leave zone III through line I6 for passage to the secondary isomerization zone I2. A liquid sludge containing aluminum Vchloride in combined and free state is formed in the primary chamber and largely drains to the bottom of the chamber, from which it is periodically or continuously withdrawn through line Il. Due to the high gas velocity through the bed of aluminum chloride in the primary chamber some sludge becomes entrainedand passes out in the gases through line I8. Normally such sludge is carried over into the secondary chamber with deleterious results. The carry-over of liquid sludge into the adsorbent of the secondary chamber causes a contamination of the secondary catalyst with consequent necessity of a premature replacement thereof.

In accordance with this invention, the eiliuent vapors from primary zone I0 are passed through a sludge-removing unit 2l in which a substantial proportion, and preferably substantially all, oi the sludge is removed by contact and reaction with limited amounts of a strong, relatively nonvolatile mineral acid, such as sulfuric acid, an oxygen-containing acid of phosphorus, especially orthophosphoric acid, or the like. Unit 20 is constructed in such a manner that very little vaporized free aluminum chloride, generally less than 10 per cent and frequently less than one or two per cent of the free AlCla vapor, is removed from the gases. One convenient construction adapted for this purpose is shown in the drawing in which a series of batlies 22 is provided. Over these baIIles is caused to flow a relatively thin illm of sulfuric acid introduced from line 24 by distributing means 26. The acid upon draining to the bottom of the chamber is removed through line 28. 'Ihe gases carrying entrained sludge, upon meeting the baies undergo suiilcient change in direction and loss in velocity as to effect a ready contact of sludge and reaction thereof with the sulfuric acid. In this manner the sludge is substantially completely removed from the vapor stream while the other components of the vapor are substantially unaffected. Hydrogen chloride and butane vapors are substantially insoluble in sulfuric acid, while the vaporized AlCh does not have much opportunity of contacting the acid in the method described. Whilel the construction shown is a preferred manner of contacting the sludge-carrying fluid with limited amounts of acid. other methods may be used. For example, the baiiles 22 may be of hollow perforated structure, with acid being forced from the hollow interior to the outside of the bafiles. A spray of coarse droplets of acid may be used to pick up the sludge without effecting too intimate a contact of fluid with acid. Other methods will occur to those skilled in the art in view of the instant disclosure of principles to be followed.

i prislng normal butane, isobutane, and hydrogen chloride. The solid adsorbent with aluminum chloride thereon acts catalytically in the presence of the hydrogen chloride to further convert normal butane to isobutane. Small amounts of sludge are formed in reactor I2 and are removed from the bottom of the chamber through line 32 as required. Conversion products which may, for example, comprise from 30 to 60 per cent isobutane, exit through line I4 for passage to the acid scrubber 3B in which residual aluminum chloride vapors are ,to be removed. However,

sludge is usually entrained in these vapors in small amounts and its introduction into the acid scrubber system 38 would be undesirable for the reasons hereinbetore` mentioned. Accordingly, the eilluent vapors are passed'through a sludge removal unit 38 which may be constructed In a manner similar to unit 2l. Sulfuric acid is supplied from line 40 through distributor 42 onto bames Ill. Any entrained sludge is removed in the manner describedabove with reference to unit 20,'and sludge-free vapors pass through line 46 into scrubber 36. Scrubber 36 is preferably fllled with'Raschig rings or other material which will promote intimate liquid-vapor contact. Acid is supplied at or near the top through line 48 and is drawn from the bottom through line 50 after passing counter-currently to the vapors. The

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blng system vla line' 1li and pass same into the,

residual sublimed aluminum chloride is completely removed from the vapors with the production of hydrogen chloride and aluminum sulfate. The so-treated vapors are passed via line of the scrubber. Aluminum sulfate is withdrawn.

from settler 52 through line 56 for any desired utilization. the system through line 58. Operation of this sulfuric acid scrubber system is more fully described in the aforementioned application Serial Make-up sulfuric acid is added tor sludge removal system as make-up acid. Aneconomical utilization of the acid is thus attained, for a smallamount of acid must be withdrawn from the scrubber system 36 in any event. Preferably, used, partially spent acid is so withdrawn from the main effluent scrubbing system comprising scrubber 88 and replaced with fresh acid i y at a rate sufficient to maintain the strength thereof above about 85 per cent1-12804. v v As an advantageous modification of the invention, thesludge withdrawn from the bottom of the reaction zones I0 and i2 is reacted with acid in conjunction with the sludge removal system. This may be done by passing such sludge to a separate contactor which is preferably supplied with sulfuric acid from settler 62 or any other suitable point-in the sludge removal system. A simpler method is shown on the drawing in which the contacting zone referred to is provided as an integral part of sludge removal unit 38. A body of acid is maintained in a lower portion thereof,

No. 460,858. Due to the substantially complete absence of sludge from the vapors passed into unit 38, the acid in this portion of the system remains of a clear color and is usedup in amounts not substantially greater than that stoichiometrlcally equivalent to the aluminum chloride vapors entering scrubber 38. The scrubber, settler, pump, and lines associated therewith remain in a clean condition for an almost indefinitely long period of time.

Acid streams from sludge removal units 20 and 88 are passed via lines 28 and 60 respectively to a common settler 62. Separate settlers may be used if desired, but are not ordinarily necessary. Aluminum sulfate accumulates in the bottom of settler 62 and acid having a lowered solids content is withdrawn from the top of settler 82 by pump 64 and passed through line 68 for rein-l troduction into the sludge removal units. Ordinarily a relatively small flow of acid over the vertical plates in theseunits is adequate to remove the sludge from vapors in a commercial isomerization plant. A slurry of aluminum sul- /fate in acid is withdrawn from the bottom'of settler 62 through line 88 to disposal or any desired utilization. The acid so withdrawn is of a dark brown or black color and may have small amounts of an insoluble oily material associated therewith. The system comprising the two sludge removal units 20 and 38 and the settler 82 together with associated pump and lines is much' smaller than the acid scrubbing system used to treat the sludge-free vaporous elliuent. Theforas shown, and an agitator 12 is provided. Sludge withdrawn from the reactors through 4 lines I8 and 32 is passed via line 14 into the body of acid for reaction therewith. Horizontal baille plates 'I6 are preferably provided slightly above the liquid level of the acid in order to minimize any carry-over of impure acid into the eiiluent scrubber unit 36. In this manner of operating, all the 'sludge formed in the process is effectively utilized to recover anhydrous hydrogen chloride therefrom, thus supplying make-up catalyst activator tothe system. .Organic components of the sludge are also recoverable in `useful form from the spent acid. The treatment of metal halide sludges with a strong, relatively nonvolatile mineral acid, such as sulfuric or phosphoric acid, is disclosed and claimed in the copending application of John W. Latchum, Jr., l,

Serial No. 516,318, filed December 30, 1943.

Asa specific example of the practice of our invention the following data are presented. Inasmuch as these data are from one particular operation, namely vapor phase butane isomerization, carried out under specicv conditions, itl

will be appreciated that the invention is of wider scope, and that this example is not to be con-' strued as unduly hunting the invention. A proc. ess for the vapor-phase isomerization of normal butane produces 25,000 gallons per day of mer system must be cleaned out more often than the latter due to its relatively large content of organic material. but this is much simpler than to clean out the larger system. Furthermore, the amount of acid in the sludge removal system is much smaller than that in the eiiluent scrubber system so that spending of acid by reaction with sludgevcontaminates and uses up a v relatively small` quantity of acid. Spent acid is withdrawn from settler 32 at a rate suicient to maintain the strength of acid in the system at a desired value, for example, at a titratable acidity of at least 50 per cent. The spent acid so withdrawn may be subjected to hydrolysis for recovery of alcohols and other'valuable materials. To replace thus-withdrawn spent acid it is necessary to introduce fresh acid intothe system. However, absolutely fresh or unused acid is not required and it is most advantageous to withdraw a bleed acid stream from the eiiluent scrubisobutane. A primary chamber I0 contains commercial aluminum chloride in lump-form, which is replenished as required, and a secondary chamber I2 contains 125 tons of Porocel." Fresh and recycle normal butane, containing `from 2 to 6 lrx'iol per cent, usually about 5' mol per cent, HCl, enters the primary at 195 F. The system'opcrates under a pressure .of pounds per square inch gage. Effluent from the primary, containing from 15 to 20 per cent isobutane, carries from 300 to 2000 lbs'. per day aluminum chloride `as, vapors and as entraixied. sludge. The sludge comes over in slugs, and thisgaccounts for the large variation in amount. The"primary eilluent vapors are next passed through a chamber constructed in a manner similar to unit 20 in the drawing for the removal of sludge. 'I'his chamber is 4' x 4 x 6 in size, and contains two vertical baille plates. Over `these plates is pumped 2000 pounds per day of sulfuric acid. 'I'he thus-treated vapors, after passingthrough a small packed towerv which prevents. any possi-blecarry-over of sulfuric acid, pass through the secondary chamber and exit therefrom at a temperature of 250 F. and with an isobutane content of from 45 to 55 per cent. These ei'iiuent vapors next pass through a second sludgeremoving Achamber of construction identical to that of the first. Sulfuric acid is pumped over the plates in the second chamber at a rate of 3000 pounds per day. l

The sludge-free vapors are next passed directly into the main acid scrubber for the complete removal of vaporized aluminum chloride. This scrubber, corresponding to unit 36 of the drawing, is a tower 4' in diameter and 15' high. and is packed to a depth of 6' with 1" Berl saddles made of stoneware. A pool of sulfuric acid is maintained below the packing into which the isomerization eiiiuents are passed, and acid is circulated from this pool to the top of the packing at a rate of 26 gallons per minute. The eilluent from the acid scrubber, which is absolutely free of AlCh in any form, is condensed and passed to the HC1 fractionator for recovery of recycle HCl. The bottoms from this fractionator are caustic Washed and then passed to the deisobutanizer column for recovery of product isobutane and recycle normal butane.

Acid is withdrawn from the main scrubber for use as make-up to the sludge removal scrubbers. Acid from the latter is passed to a separate batch contactor into which is introduced, onv the average, about 500 pounds per day of sludge withdrawn from the bottom of the primary and secondary chambers. 'I'his `contactor is held at about 140 pounds per square inch gage, and is operated at 150 F'. HC1 is produced at the rate of 220 pounds per day and is pressured from the contactor into the HC1 fractionator feed tank as needed. Of course additional make-up HCl is continuously added to the system by reaction of sludge and vaporized AlCla in the three acid contactors through which the vapor stream passes.

The principal acid scrubber remains in an exceptionally clean condition, and the acid therein is only slightly darkened in color. The rate of withdrawal of acidfrom this system to the sludge removal system, and from the sludge removal system to the batch sludge contacter, is more than adequate to maintain a high acid concentration in and to give satisfactory functioning of the vapor-treating units, The over-all acid-consump tion is, also substantially reduced compared to the acid consumption in a similar system not employ` ing the sludge removal units. A

We claim:

1. A process for' isomerizing normal butane to isobutane which comprises passing a gaseous' stream comprising normal butane and a catalystactivating'amount o'f hydrogen chloride through afirst zone containing an aluminum chloride isomerization catalyst, removing therefrom a gaseous stream containing volatilized aluminum chloride and also containing liquid aluminum Cil therein, contacting said stream with a limited amount of a strong, relatively non-volatile mineral acid under conditions eiiecting removal of a ysubstantial proportion ofsaid entrained sludge by contact and reaction with said acid without removing volatilized aluminum chloride to more than a minor extent, passing the .so-treated stream into contact with sufiicient strong, relatively non-volatile mineral acid to substantially remove said volatilized aluminum chloride therefrom, and recovering isobutane product from the so-treated stream.

2. The process of claim 1, in which said strong, relatively non-volatile mineral acid used in each of said acid-contacting steps is sulfuric acid.

3. The process of claim l, in which said strong, relatively non-volatile mineral acid used in each of said acid-contacting steps is phosphoric acid.

- 4. The process of claim 1, in which acid from each of said rst two acid-contacting steps is passed to a common settling zone, an insoluble aluminum salt is removed from the acid by settling therein, and acid is yreturned from said settling zone to said first two acid-contacting steps.

5. The process of claim l, in which acid from each of said first two acid-contacting steps is used to react with additional aluminum chloride sludge removed from said first and second zones, and hydrogen chloride formed by said reaction is introduced into the isomerization system as catalyst activator.

6. In a process in which a reaction eiiluent is obtained from a hydrocarbon conversion catalyzed by a metal halide catalyst of the Friedel- Crafts type, which eilluent contains a substantial ,amount of said catalyst in sludge form and also in the free state in non-,sludge form, and in which saidv eiliuent is treated with a strong, relatively non-volatile mineral acid to eiect removal of said `catalyst therefrom, the improvement which comprises contacting said eiiluent in a first step with a iirst portion of said acid in limited amount under conditions eiecting removal of a substantially higher percentage of the total sludge present in said eiiluent than of the total catalyst in nonsludge form present in said eiiluent, and then contacting said eiiiuent in a second step with a second and different portion of said acid in an amount and under conditions adequate to effect substantial removal of remaining catalyst.

7. The process of claim 6, in which used, partially spent acid is removed from said second portion of acid and introduced as make-up into said rst portion of acid.

8. In the vapor phase conversion of low-boiling paramn hydrocarbons in the presence of a. Friedel-Crafts type metal halide catalyst, in which l vaporous conversion iiiuents containing vaporchloride sludge entrained therein, contacting said stream with a limited amount of a strong, relatively non-volatile mineral v-acid under conditions effecting removal of a substantial proportion of said entrained sludge by contact and reaction with said acid without removing volatilized a1u' minum chloride to more than a minor extent, passing the so-treated stream at isomerization conditions through a second zone containing an isomerization catalyst comprising aluminum chlorideadsorbed on a solid adsorbent material, removing therefrom a gaseous stream containing volatilized aluminum chloride and also containing liquid aluminum chloride sludge entrained ized metal halide catalyst and also entrained liquid metal halide-hydrocarbon sludge are contacted with sulfuric acid to substantially completely remove catalyst therefrom, the improved method of operating with comprises contacting. said vaporous eiiluents with ya limited amount of' sulfuric acid under conditions eiiecting substantially complete removal of sludge therefrom but incomplete removal of vaporized catalyst, and then contacting resulting sludge-free eiiluents with a body of sulfuric acid to effect substantially complete removal of remaining metal halide catalyst' therefrom, acid being used in said latter body of sulfuric acid being maintained separate from acid being used in said sludge-removal step, thereby avoiding contamination of said body of acid with organic constituents of said sludge.

9. In the process oi claim 8, withdrawing acid from said body of acid and supplying fresh acid thereto at a rate sufficient to maintain the strength thereof above about 85 per cent H3804, and passing acid so withdrawn to said sludze removal step to replace acid removed by reaction with said sludge.

10. In the isomerization 'of normal butane to isobutane wherein a normal butane-containing gas is passed at elevated temperature in contact with solid aluminum chloride to pick up sublimed aluminum chloride, and then passed at isomerization conditions of temperature andv pressure in contact with a solid adsorbent material which is maintained active as an isomerization catalyst by adsorption of said sublimed aluminum chloride from said gas, and wherein an aluminum chloride sludge is entrained in said gas upon contact f said gas with said solid 'aluminum chloride and is carried into contact with said solid adsorbent with deleterious effect, the method of protecting said solid adsorbent -froin contamination with said sludge which comprises contacting said gas, at a point intermediate its contact with said. solid aluminum chloride and its contact with said solid adsorbent, with a limited amount of sulfuric acid under conditions effecting substantially complete removal of said entrained sludge while avoiding removal of more than about 10 per cent of said subllmed aluminum chloride.

11. The process vof claim 6, in which said strong, relatively non-volatile mineral acid is sulfuric acid. 4

12. 'I'he process of claim 6, in which said strong, relatively non-volatile mineral acid is an ommen-containing acid of phosphorus.

13. The process of claim 6, in vwhich said strong, relatively non-volatile mineral acid is orthophosphoric acid.

14. The process of claim 6. in which metal halide sludge in addition to that contained in and removed from said eiilue'nt as described is obtained from said conversion, is reacted with used. partially spent acid from at least one oi said acid-contacting steps. and hydrogen halide so 'formed by said reaction is introduced into the A conversion as catalyst activator.

JOHN w. LATCHUM, su. JOHN D. opium. 

